The diagnosis and treatment of prostate cancer, despite decennial research efforts, are still a major challenge in the clinics. Prostate cancer progression is unfortunately silent, and an early detection of faster progressing and potentially dangerous lesions is crucial for the patient's health, since complete remission and cure from the disease is possible only at early stages of the disease.
The best noninvasive diagnostic test available for prostate cancer is the detection of the Prostate Specific Antigen (PSA) in the blood coupled with digital rectal examination (DRE). PSA is a protein produced by the epithelial cells of the prostate gland. PSA is also known as kallikrein III, seminin, semenogelase, γ-seminoprotein and P-30 antigen and it is a 34 kD glycoprotein present in small quantities in the serum of normal men, and is often elevated in the presence of prostate cancer and in other prostate disorders. A blood test to measure PSA coupled with DRE is the most effective test currently available for the early detection of prostate cancer. Higher-than-normal levels of PSA are associated with both localized (loc) and metastatic (met) prostate cancer (CaP).
The diagnostic accuracy of PSA alone is only around 60% and the methodology has major drawbacks in specificity (too many false positives cases that undergo unneeded prostate biopsy or surgery). Indeed PSA levels can be also increased by prostate infection, irritation, benign prostatic hypertrophy (enlargement) or hyperplasia (BPH), and recent ejaculation, producing a false positive result.
A reliable and non-invasive diagnostic/prognostic procedure is thus still lacking, even tough novel methodologies based on the simultaneous measurement of various parameters (e.g. free and total PSA) are emerging as tools to increase the overall diagnostic accuracy. Most PSA in the blood is bound to serum proteins. A small amount is not protein bound and is called free PSA. In men with prostate cancer the ratio of free (unbound) PSA to total PSA is decreased. The risk of cancer increases if the free to total ratio is less than 25%. The lower the ratio, the greater the probability of prostate cancer. However, both total and free PSA increase immediately after ejaculation, returning slowly to baseline levels within 24 hours, and also other mechanisms not related to CaP can influence the free to total PSA ratio.
Similar to diagnosis, treatment and/or prognosis of prostate cancer remains a major challenge due to heterogeneity of the disease. Although multiple mechanisms of prostate cancer have been suggested, the lack of suitable signatures able to stratify patients and key target proteins for therapeutic intervention cures are still not within reach.